Synthetic (plastic) fibers which contract and expand upon stimulation with acid, heat, electrical current and light have been known for some time, see the article by Y. Osada, entitled "Conversion of Chemical into Mechanical Energy by Synthetic Polymers," Adv. in Polym. Sci 82, Springer Verlag, Berlin, Heidelberg, 1987. However, a good mimic of the human or animal muscle by a natural or synthetic fiber has been difficult to say the least since there has been no way to distribute the muscle-activating energy quickly to the fibers to enable responsive motion.
Thus, a continuing need exists in the state of the art for a means of supplying activating energy to natural or synthetic fibers, such as polyelectrolyte fibers or gels, which respond to pH changes in a pH dependent solution by changing their volume, thereby enabling the fibers to do work in response to selected wavelengths of impinging electromagnetic radiation.